Conducting properties of In2O3:Sn thin films at low temperaturesстатья
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Дата последнего поиска статьи во внешних источниках: 30 апреля 2014 г.
Аннотация:Electrical conductivity, Hall effect and magnetoresistance
of In2O3:Sn thin films deposited on a glass substrates
at different temperatures and oxygen pressures, have
been investigated in the temperature range 4.2–300 K. The
observed temperature dependences of resistivity for films
deposited at 230 °C as well as at nominally room temperatures
were typical for metallic transport of electrons except
temperature dependence of resistivity of the In2O3:Sn film
deposited in the oxygen deficient atmosphere. The electrical
measurements were accompanied by AFM and SEM studies
of structural properties, as well as by XPS analysis. It is
established that changes of morphology and crystallinity of
ITO films modify the low-temperature behavior of resistivity,
which still remains typical for metallic transport. This is
not the case for the oxygen deficient ITO layer. XPS analysis
shows that grown in situ oxygen deficient ITO films
have enhanced DOS between the Fermi level and the valence
band edge. The extra localized states behave as acceptors
leading to a compensation of n-type ITO. That can explain
lower n-type conductivity in this material crossing over to a
Mott-type hopping at low temperatures. Results for the low
temperature measurements of stoichiometric ITO layers indicate
that they do not show any trace of metal-to-insulator
transition even at 4.2 K. We conclude that, although ITO is
considered as a highly doped wide-band gap semiconductor,
its low-temperature properties are very different from those
of conventional highly doped semiconductors.